Generate all finite sequences of letters (a-z)

gistfile1.rb

def each_str
  l = 0
  while true
    s = 'a' * (l + 1)
    while true
      yield s
      if s[l] == 'z'
        i = l
        i -= 1 while s[i] == 'z' && i >= 0
        if i >= 0
          s[i] = (s[i].ord + 1).chr
          (i + 1).upto(l) {|ii| s[ii] = 'a' }
          i = l
        else
          break
        end
      else
        s[l] = (s[l].ord + 1).chr
      end
    end
    l += 1
  end
end

gistfile2.hs

concat $ map (`replicateM` ['a'..'z']) [1..]